www.tvSmarter.com – Life in a TV Nation

Dopamine and Addiction

Drug addiction, addiction to gambling, and food and video games and TV, all have dopamine as the common denominator:

“The brain registers all pleasures in the same way, whether they originate with a psychoactive drug, a monetary reward, a sexual encounter, or a satisfying meal. In the brain, pleasure has a distinct signature: the release of the neurotransmitter dopamine in the nucleus accumbens, a cluster of nerve cells lying underneath the cerebral cortex (see illustration). Dopamine release in the nucleus accumbens is so consistently tied with pleasure that neuroscientists refer to the region as the brain’s pleasure center.

All drugs of abuse, from nicotine to heroin, cause a particularly powerful surge of dopamine in the nucleus accumbens. The likelihood that the use of a drug or participation in a rewarding activity will lead to addiction is directly linked to the speed with which it promotes dopamine release, the intensity of that release, and the reliability of that release.”

“Does this mean that people can’t have problem usage of video games? No. But what it does mean, in my opinion, is that we have to stop treating behaviors as if they were controlled substances. Playing video games, watching television, eating, and having sex are behaviors that can all be problematic in certain times and certain contexts. But they are not the same as ingesting drugs, they don’t cause the same level of chemical change in the brain.”

True enough, but as “Joe” in comments points out:

“If the peak dopamine exposure from video games is indeed roughly a 100% increase above baseline or normal level while playing, then the cumulative exposure above baseline over several hours daily (as is common for kids playing video games) rivals the cumulative extra exposure from some of the drugs in the charts above. For example from the charts above, 10 mg/kg morphine causes release 100% above baseline for 2 hrs and 50% above for ~1 hr while cocaine averages ~150% above baseline for 4 hrs. If we compare this to video gaming at 100% above baseline, then the exposure above baseline from 2 to 3 hours of video games is similar to the 10 mg/kg of morphine and 4 to 6 hours is comparable to cocaine. And while one might deplete cash fast with daily hits of morphine or cocaine, video games are cheap and easily accessible enough to be used daily.”

“Continuous use of such drugs robs them of their power to induce euphoria. Addictive substances keep the brain so awash in dopamine that it eventually adapts by producing less of the molecule and becoming less responsive to its effects. As a consequence, addicts build up a tolerance to a drug, needing larger and larger amounts to get high. In severe addiction, people also go through withdrawal—they feel physically ill, cannot sleep and shake uncontrollably—if their brain is deprived of a dopamine-stimulating substance for too long. At the same time, neural pathways connecting the reward circuit to the prefrontal cortex weaken. Resting just above and behind the eyes, the prefrontal cortex helps people tame impulses. In other words, the more an addict uses a drug, the harder it becomes to stop.”

“Lower levels of dopamine D2 receptor availability have been previously reported in cocaine abusers, alcoholics, and heroine abusers. This study extends this finding to methamphetamine abusers. The association between level of dopamine D2 receptors and metabolism in the orbitofrontal cortex in methamphetamine abusers, which replicates previous findings in cocaine abusers, suggests that D2 receptor-mediated dysregulation of the orbitofrontal cortex could underlie a common mechanism for loss of control and compulsive drug intake in drug-addicted subjects.”

“The research by Johnson and Kenny examined whether exposure to the kind of high-fat, super high-calorie foods that floods the junk-food market are responsible for creating food-addicts in a similar way to drugs that alter the brain in ways that make stopping more difficult.”

“When the researchers looked deeper, they found that the brains of these rats suffered a significant reduction in the density of a specific kind of dopamine receptor (D2) in a brain part known as the striatum, the same kind of reduction common in drug addicted people and obese individuals. This receptor type is often thought to be important for regulation of impulses, both physical and otherwise. It therefore makes sense that losing this type of function would cause uncontrollable eating or drug taking.”

“While this research isn’t saying that compulsive eating, or obesity, are the same as drug addiction, it does strongly suggest that there are common mechanisms in both. More importantly, it reveals a common process that unfolds when over-exposure to the reward, in this case food, occurs. This tells us that there can likely be common pathways to these different addictive disorders…”

So what about the mice who where way over-exposed to TV during their childhood? Did they suffer from the same kind of reduction of dopamine receptor (D2)? Unfortunately the mouse TV study didn’t check, but it did find that the over-exposed mice were greater risk-takers (more impulsive).

“People with high levels of the hormone dopamine in the brain, and low sensitivity to it, tend to be greater risk takers and may be more prone to addictive behavior, drug abuse and gambling, a study has found.”

But a new study finds that the brain of those with addictions and those with ADHD are quite different:

“The findings also showed that although participants with ADHD had significantly less grey matter in the brain, and performed much worse in the attention tests than the healthy controls, they had similar levels of dopamine receptors in an area of the brain called the striatum. Ritalin raised dopamine levels in this area to the same degree.”

Since both addiction and ADHD are associated with risky behavior, it would be very interesting if the mouse study were replicated with the addition of analyzing the TV mice brains to see if how they compare with regular mice, addicted mice and ADHD mice.